#include <iostream>
using namespace std;

string a, b;
void dfs(int l1, int r1, int l2, int r2)
{
    if(l1 > r1) return;
    
    int p = l1;
    
    while(a[p] != b[l2]) p++;
    dfs(l1, p - 1, l2 + 1, l2 + p - l1);
    dfs(p + 1, r1, l2 + p - l1 + 1, r2);
    
    cout << b[l2];
}
int main()
{
    cin >> a >> b;
    dfs(0, a.size() - 1, 0, b.size() - 1);
    return 0;
}